Method of blackening a steel component for a color cathode ray tube

ABSTRACT

The steel components of a cathode ray tube, mainly the aperture mask and the aperture mask frame are blackened by immersing the same in an electroless plating bath selected from the group consisting of nickel and cobalt and after subsequent rinses immersing again in a strong oxidizing acid and firing the component in air at about 450*C to form a black, complex nickel or cobalt compound on the surface of the component.

nited States Patent Decker et al.

[451 Feb. 18, 1975 METHOD OF BLACKENING A STEEL COMPONENT FOR A COLORCATHODE RAY TUBE Inventors: John J. Decker; Susan V. Zito, both ofEmporium, Pa.

GTE Sylvania Incorporated, Stamford, Conn.

Filed: May 29, 1973 Appl. No.1 364,975

Assignee:

U.S. Cl. l48/6.l4 R, 148/615 R, 117/130 E Int. Cl. C23f 5/02 Field ofSearch 117/130 E; 148/63, 6.14,

References Cited UNITED STATES PATENTS 5/1958 Bolin 117/130 E 3,088,8465/1963 Lee [17/71 M Primary Examiner-Leon D. Rosdol AssistantExaminerCharles R. Wolfe, Jr. Attorney, Agent, or Firm-Norman J.OMalley; William H. McNeill; Donald R. Castle [57] ABSTRACT 4 Claims, NoDrawings METHOD OF BLACKENING A STEEL COMPONENT FOR A COLOR CATHODE RAYTUBE BACKGROUND OF THE INVENTION This invention relates generally to theaperture mask and aperture mask frames of color picture tubes and moreparticularly to a method of applying thereto a black surface coating. Ithas been common practice for many years to blacken the surface of theaperture mask and aperture mask frame of a color picture tube to providebetter heat radiation characteristics. Generally, this has beenaccomplished by merely firing the frames or masks in a wet atmosphere.This process generally yields a black oxide of iron; however, manydisadvantages are present in this process. For example, under manyconditions a brown oxide of iron is formed either during the processitself or at some point in time during the storage of the component.Further, iron oxide has a tendency to decompose in a vacuum when it isheated and bombarded with electrons as is the case during operation ofthe color cathode ray tube in which it is employed.

Therefore, it would be advantageous if a process could be found whichwould blacken these steel components without having the disadvantages ofthe prior art techniques.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, an object of thisinvention to obviate the disadvantages of the prior art.

It is another object of the invention to provide a simple and reliablemethod of blackening steel components of color cathode ray tubes.

It is yet another object of the invention to provide a stable blackenedsurface upon the steel components of a color cathode ray tube,

These objects are accomplished in one aspect of the invention by theprovision of a method whereby the steel components of a color cathoderay tube, such as the aperture mask frame and the aperture mask itself,are provided with a nickel or cobalt compoundcoating from an electrolessplating bath and subjecting this coating to a strong oxidizing acid andsubsequently firing the same in air at about 450C to provide a complexblack nickel or cobalt compound upon the surface. The

compound formed by this process is extremely stable and has shown theadvantage of remaining black even after many passes at about 450C in anair atmosphere.

It is believed that the black nickel or cobalt compound formed on thesurface is a nickel or cobalt phosphide having the formula Ni P or Co P.

DESCRIPTION OF THE PREFERRED EMBODIMENTS ponent is next placed in anelectroless nickel or cobalt plating bath for about 15 minutes. A numberof such electroless nickel plating baths are commercially available andexcellent results have been had with a bath known as Shipley NL-62,which is available from the Shipley Company, Newton, Mass. A number ofother nickel plating baths both acid and alkaline are disclosed in US.Pat. No. 2,532,283. Additionally, cobalt plating baths are disclosed inUS. Pat. No. 2,532,284.

A particularly workable nickel plating bath is composed of 30 grams perliter of nickel chloride, 50 grams per liter of sodium glycollate, and10 grams per liter of sodium hypophosphite. The pH of the plating bathshould be between 4 and 6 and the temperature of the bath should beabout l9()F. If necessary the pH can be adjusted by the addition ofsodium hydroxide.

A suitable cobalt plating bath is composed of 30 grams per liter ofcobalt chloride, 35 grams per liter of sodium citrate, 50 grams perliter of ammonium chloride and 20 grams per liter of sodiumhypophosphite. As this is an alkaline bath the pH should be about 9-10and the temperature about lF to 205F. If necessary, the pH can beadjusted by addition of ammonium hydroxide.

After immersion in the electroless nickel or cobalt plating bath whichas has been mentioned above, should be for about 15 minutes. thecomponent is removed from the bath and rinsed in deionized water. Next,the component is immersed in a strong oxidizing acid for 30 to 45seconds. A suitable oxidizing acid contains 3 parts phosphoric, 1 partsulfuric, and 1 part nitric, all in concentrated form. After theoxidizing acid bath the component is removed and quickly rinsed in warmtap water. Further rinses are then performed in deionized water, andanhydrol. The component is then dried and fired for about 1 hour in airat about 450C.

As stated above, the black surface coating that is now formed on thecomponent is a complex nickel or cobalt compound which is believed to beNi P or Co P, that is, a nickel or cobalt phosphide. These compoundshave been found to be extremely stable during the various processingprocedures used to fabricate a cathode ray tube, and these proceduresinvolve numerous bak ings in air at above 400C. Furthermore, eithercoating is very stable during operation of the cathode ray tube in whichthe component is incorporated even though it is being bombarded withelectrons in a vacuum and is subject to repeated heating and cooling.

It will be seen from the above that use of this process obviates many ofthe disadvantages of the prior art and when applied to the aperture maskframe or the aperture mask itself of a color cathode ray tube has manyunique properties.

While there has been shown what is at present considered to be thepreferred embodiments of the invention, it will be apparent to thoseskilled in the art that various changes and modifications can be madeherein without departing from the scope of the invention as defined bythe appended claims.

What is claimed is:

l. A method of blackening a steel component which comprises the stepsof: degreasing said component; immersing said component in a 50%hydrochloric acid bath for about 1 minute; rinsing said component indeionized water; immersing said component in an electro less platingbath selected from the group consisting of nickel or cobalt for about 15minutes, said plating bath 2. The method of claim 1 wherein saidcomponent is a steel frame of an aperture mask.

3. The method of claim 1 wherein said component is a steel aperturemask.

4. The method of claim 1 wherein said oxidizing acid is comprised of 3parts phosphoric, 1 part sulfuric, and 1 part nitric acid.

1. A METHOD OF BLACKENING A STEEL COMPONENT WHICH COMPRISES THE STEPSOF: DEGREASING SAID COMPONENT; IMMERSING SAID COMPONENT IN A 50%HYDROCHLORIC ACID BATH FOR ABOUT 1 MINUTE; RINSING SAID COMPONENT ISDEIONIZED WATER; IMMERSING SAID COMPONENT IN AN ELECTROLESS PLATING BATHSELECTED FROM THE GROUP CONSISTING OF NICKEL OF COBATH FOR ABOUT 15MINUTES, SAID PLATING BATH INCLUDING AN EFFECTIVE AMOUNT OF A REDUCINGAGENT INCLUDING A HYPOPHOSPHITE COMPOUND; RINSING SAID COMPONENT INDEIONIZED WATER; IMMERSING SAID COMPONENT IN A STRONG OXIDING ACID BATHFOR 30 TO 45 SECONDS, RINSING SAID COMPONENT IN WARM TAP WATER;RERINSING SAID COMPONENT IN DEIONIZED WATER; RERINSING SAID COMPONENT INANHYDROL; DRYING SAID COMPONENT; AND FIRING SAID COMPONENT IN AIR FORABOUT 1 HOUR AT ABOUT 450*C.
 2. The method of claim 1 wherein saidcomponent is a steel frame of an aperture mask.
 3. The method of claim 1wherein said component is a steel aperture mask.
 4. The method of claim1 wherein said oxidizing acid is comprised of 3 parts phosphoric, 1 partsulfuric, and 1 part nitric acid.